I was raising questions. Any inferences are not put there by me.
I fully accept that NO ONE should EVER move someone elses car. I have had exactly the same done to my bike once (but not at school - at someones house. Their son moved the bike and never mentioned it when I came back into the house crying because I thought my bike had been stolen. We didnt find the bike until the next day 0 in their shed!. I had to get a lift home, while the son who had moved the bike sat in the kitchen watching me cry and phone my partner for a lift home).
Im just questioning whether sueing would be the best idea. Personally, I would make a written compalint to school, to the Local Education Authority and move my son to another school. And I wouldnt lend my car to a person who leaves the keys inside. But I think sueing is a sledgehammer to crack a nut. And I think saying the car was stolen is not quite true.